When an A-D converter that has a high accuracy and is of a ΔΣ type is used to sense a battery voltage that is a voltage of a battery, it is necessary that an oversampling is executed in the A-D converter of a ΔΣ type. Then, a charge and discharge of a capacitor is repeated at a short cycle, and a leakage current that is a current leaked from the battery that is a sensing target is generated. In a system sensing the battery voltage, a low-pass filter including a capacitor and a resistance having a relatively high resistance value is arranged in an input region. Thus, a decrease of a voltage generated due to the leakage current flowing through the resistance of the low-pass filter leads to an error in a sensing result, and the decrease cannot be ignored with respect to a sensing value of the voltage.
According to US2012-0274360, a compensation circuit that generates a compensation current flowing in a direction opposite to a direction in which the leakage current flows is provided, and then the leakage current is cancelled. Thus, the error of the sensing result generated due to the decrease of the voltage generated by the resistance of the low-pass filter is reduced.